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Observer for Swing JPanel

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  Observer for Swing JPanel "thufir" <thufir@THRWHITE.remove-dii-this> - 2011-04-27 15:48 +0000
    Re: Observer for Swing JP "Mark Space" <mark.space@THRWHITE.remove-dii-this> - 2011-04-27 15:48 +0000
      Re: Observer for Swing JP "thufir" <thufir@THRWHITE.remove-dii-this> - 2011-04-27 15:48 +0000

#3996 — Observer for Swing JPanel

  To: comp.lang.java.gui,comp.l
Follow up to comp.lang.java.gui

Given that SourceTableBean extends JPanel, how can SourceTableBean send 
messages to Main?  Or, to turn that question around, how can Main listen 
for events which SourceTableBean sends?  How does the JFrame observe the 
JPanel?

No, this, intentionally, isn't a single class.  By definition, working on 
multiple files:

thufir@arrakis:~/code$ cat beans/src/Main.java 

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

public class Main extends javax.swing.JFrame /*implements 
PropertyChangeListener*/ {

    public Main() {
        initComponents();
    }

    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-
BEGIN:initComponents
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        text = new javax.swing.JTextArea();
        table = new SourceTableBean();

        setDefaultCloseOperation
(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        text.setColumns(20);
        text.setRows(5);
        jScrollPane1.setViewportView(text);

        getContentPane().add(jScrollPane1, java.awt.BorderLayout.NORTH);

        /*
        table.addPropertyChangeListener(new 
java.beans.PropertyChangeListener() {
            public void propertyChange(java.beans.PropertyChangeEvent 
evt) {
                tablePropertyChange(evt);
            }
        });*/

        //table.addPropertyChangeListener(this);
        getContentPane().add(table, java.awt.BorderLayout.CENTER);

        pack();
    }// </editor-fold>//GEN-END:initComponents

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new Main().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JScrollPane jScrollPane1;
    private SourceTableBean table;
    private javax.swing.JTextArea text;
    // End of variables declaration//GEN-END:variables

}
thufir@arrakis:~/code$ 
thufir@arrakis:~/code$ cat beans/src/SourceTableBean.java 

import java.beans.PropertyChangeSupport;

public class SourceTableBean extends javax.swing.JPanel {
    //pcs = new java.beans.PropertyChangeSupport(this);
    //PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    public SourceTableBean() {
        initComponents();
    }

    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-
BEGIN:initComponents
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        table = new javax.swing.JTable();

        setLayout(new java.awt.BorderLayout());

        table.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {"a0", "a1", "a2", "a3"},
                {"b0", "b1", "b2", "b3"}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        table.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                tableMouseClicked(evt);
            }
        });
        jScrollPane1.setViewportView(table);

        add(jScrollPane1, java.awt.BorderLayout.CENTER);
    }// </editor-fold>//GEN-END:initComponents
    private void tableMouseClicked(java.awt.event.MouseEvent evt) {//GEN-
FIRST:event_tableMouseClicked
        System.out.println("\nSourceTableBean.tableMouseClicked()\t");
        int row = table.getSelectedRow();
        int col = table.getSelectedColumn();
        String val = table.getValueAt(row, col).toString();
        System.out.println("how to send " + val + " to main?");
        
    }//GEN-LAST:event_tableMouseClicked

        
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable table;
    // End of variables declaration//GEN-END:variables
}
thufir@arrakis:~/code$ 



thanks,

Thufir

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#4001 — Re: Observer for Swing JP

  To: comp.lang.java.gui
thufir wrote:
> Follow up to comp.lang.java.gui
> 
> Given that SourceTableBean extends JPanel, how can SourceTableBean send 
> messages to Main?  Or, to turn that question around, how can Main listen 
> for events which SourceTableBean sends?  How does the JFrame observe the 
> JPanel?

Well, one way to do this would be to add the bean you made to the GUI 
builder palette.

<http://java.sun.com/docs/books/tutorial/javabeans/nb/index.html>


Another would be just to added the bean to the class in the constructor, 
like below.

> public class Main extends javax.swing.JFrame /*implements 
> PropertyChangeListener*/ {

   private SourceTableBean stb;
> 
>     public Main() {
>         initComponents();

           stb = new SourceTableBean();
           stb.addPropertyChangeListener( this );//Main must implement
                                                 //PropertyChangeListener
                                                 //for this to work.
           add( stb );  // or some way to add to layout
           pack();      // repack since we've changed layout
>     }



Another would be to make a third class that's responsible for starting 
up the GUI.  This class has a method to bind the Main instance to the 
SourceTableBean instance. Note that you really should be creating the 
GUI on the EDT, it's the only safe way to do it. Consider making the 
constructor of Main package private to enforce this.

public class StartHere {

   public static void createAndShowGUI() {

     java.awt.EventQueue.invokeAndWait( new Runnable() {
        @Override
        public void run() {
          Main m = new Main();
          SourceTableBean stb = new SourceTableBean();
           stb.addPropertyChangeListener( m); // Main must implement
                                              // PropertyChangeListener
                                              // for this to work.
           m.add( stb );  // or some way to add to layout
           m.pack();      // repack since we've changed layout
           m.setVisible( true );
         }
     } );
   }
}


Not compiled, beware of unbalanced braces.  Also, I have no idea why you 
want to use PropertyChangeListeners.  I think there might be a better 
way of doing this.  Look at the type of events PropertyChangeLister. 
Look at the types of events they handle for a JPanel (it's under 
java.awt.Container, I think) and they're really low-level GUI type 
events.  Possibly you want something higher level.

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#4009 — Re: Observer for Swing JP

  To: comp.lang.java.gui
On Fri, 15 Aug 2008 18:44:30 -0700, Mark Space wrote:


> Not compiled, beware of unbalanced braces.  Also, I have no idea why you
> want to use PropertyChangeListeners.  I think there might be a better
> way of doing this.

What I came up with, which works but is, to me, black magic:


thufir@arrakis:~/beans$ 
thufir@arrakis:~/beans$ cat beans/src/SourceTableBean.java 

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;

public class SourceTableBean extends javax.swing.JPanel /*implements 
PropertyChangeListener*/ {

    int currentRow = 1;
    //private final PropertyChangeSupport pcs = new PropertyChangeSupport
(this);

    public SourceTableBean() {
        initComponents();
    }

    public void setCurrentRow(int newRow) {
        int oldRow = currentRow;
        currentRow = newRow;
        //pcs.firePropertyChange("row", oldRow, newRow);
        this.firePropertyChange("row", oldRow, newRow);
    }

    
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-
BEGIN:initComponents
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        table = new javax.swing.JTable();

        setLayout(new java.awt.BorderLayout());

        table.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {"a0", "a1", "a2", "a3"},
                {"b0", "b1", "b2", "b3"}
            },
            new String [] {
                "Title 1", "Title 2", "Title 3", "Title 4"
            }
        ));
        table.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                tableMouseClicked(evt);
            }
        });
        jScrollPane1.setViewportView(table);

        add(jScrollPane1, java.awt.BorderLayout.CENTER);
    }// </editor-fold>//GEN-END:initComponents
    private void tableMouseClicked(java.awt.event.MouseEvent evt) {//GEN-
FIRST:event_tableMouseClicked
        int row = table.getSelectedRow();
        setCurrentRow(row);        
    }//GEN-LAST:event_tableMouseClicked
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTable table;
    // End of variables declaration//GEN-END:variables
}
thufir@arrakis:~/beans$ 
thufir@arrakis:~/beans$ cat beans/src/Main.java 

import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;

public class Main extends javax.swing.JFrame /*implements 
PropertyChangeListener*/ {

    public Main() {
        initComponents();
    }

    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-
BEGIN:initComponents
    private void initComponents() {

        jScrollPane1 = new javax.swing.JScrollPane();
        text = new javax.swing.JTextArea();
        table = new SourceTableBean();

        setDefaultCloseOperation
(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        text.setColumns(20);
        text.setRows(5);
        jScrollPane1.setViewportView(text);

        getContentPane().add(jScrollPane1, java.awt.BorderLayout.NORTH);

        table.addPropertyChangeListener(new 
java.beans.PropertyChangeListener() {
            public void propertyChange(java.beans.PropertyChangeEvent 
evt) {
                tablePropertyChange(evt);
            }
        });
        getContentPane().add(table, java.awt.BorderLayout.CENTER);

        pack();
    }// </editor-fold>//GEN-END:initComponents
    private void tablePropertyChange(java.beans.PropertyChangeEvent evt) 
{//GEN-FIRST:event_tablePropertyChange
        System.out.println("\nproperty changed\t" + evt.getPropertyName() 
+ "\t" + evt.getNewValue().toString());
    }//GEN-LAST:event_tablePropertyChange

    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new Main().setVisible(true);
            }
        });
    }
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JScrollPane jScrollPane1;
    private SourceTableBean table;
    private javax.swing.JTextArea text;
    // End of variables declaration//GEN-END:variables
}
thufir@arrakis:~/beans$ 



I'm not totally sure that it's reliable, there seems to be a delay in 
registering user clicks -- but I'll live with that.  I think that a 
PropertyChangeSupport object would be useful for more complex situations, 
such as if the SourceBean had multiple buttons.

Please do critique!  I just need to bang out some code for now, but would 
like to know if there's a better way.  I didn't get a chance to look at 
your solution wrt to constructors, yet...



-Thufir

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